This research proposal is designed to investigate the development of the nervous system of the lungs of fetal, neonatal and adult rabbits and the effects of vagotomy on the neonatal rabbit lungs. The lung specimens will include fetuses of gestational ages between 15-31 days; and neonatal, mature and vagotomized rabbits. These lungs will be studied with electron microscopy, silver stain, cholinesterase histochemistry, and fluorescent technique as well as surfactant assay with bubble stability ratio and thin layer chromatography. The silver stain will reveal the general distribution pattern of the autonomic ganglia and the nerves along the pulmonary airways and the blood vessels. The cholinesterase histochemistry will specifically show the locations of the parasympathetic cholinergic nerves. The fluorescent microscopy will illustrate the sympathetic adrenergic nerves. Electron microscopy will be used to study the fine relationships between the sensory and the motor nerves and their receptor and effector cells such as the smooth muscle and the glands, and also to show the changes of the nerves and the cells of the lungs after vagotomy. The bubble stability ratio and thin layer chromatography will evaluate the degree of maturation or deficiency of the surfactant system in the developing or vagotomized lungs. The surfactant assay methods coupled with electron microscopic observations of the normal and vagotomized animals will provide additional information concerning the surfactant system, the activities of the type II pneumocytes and the roles of the nervous system in the development and the normal functions of the lungs. It is anticipated that the results of this research project will significantly contribute to knowledge of the mechanism of respiration and functions of the lungs.